Magnetic device

ABSTRACT

A magnetic device for being used in a driver is provided. The magnetic device includes a permanent magnet unit, a first yoke unit positioned corresponding to the permanent magnet unit, a second yoke unit having one end connected with the first yoke unit, and a coil complex having a double-cross type for generating magnetic force, wherein the permanent magnet unit, the first yoke unit and the second yoke unit are used for generating a magnetic circuit, and the magnetic force generated from the coil complex interacts with the magnetic circuit.

FIELD OF THE INVENTION

[0001] The present invention relates to a magnetic device, and moreparticularly to a magnetic device for being used in a read/write head.

BACKGROUND OF THE INVENTION

[0002] Generally, data-recording media for accessing and recording thedata are supported by drivers. The magnetic recording devices, forexample, soft discs or hard discs, have drivers for magnetic read/writeheads. The optical recording devices, for example, CD, VCD or DVD, havecorresponding drivers for optical read/write heads. In addition, MO orMD has corresponding drivers for read/write heads. The drivers are usedfor precisely directing the read/write heads to the working positions.

[0003] FIGS. 1 to 4 are schematic views showing the conventionalobjective lens drivers. According to the movable member V of theconventional objective lens drivers, the drivers are divided into twotypes as follows.

[0004] a) moving coils: the movable member V has a focusing coil F1 andperpendicular tracking coils T1, T2 and T3 thereon as shown in FIGS. 1to 3.

[0005] b) moving magnets: the movable member V has permanent magnets M1and M2 thereon as shown in FIG. 4.

[0006] However, the theories applied in the drivers are similar. Themagnetic field generated by the permanent magnets M1 and M2 and theyokes Y1, Y2 and Y3. When electric current passes through the focusingcoils F1 and F2 or the tracking coils T1, T2 and T3, another variablemagnetic field is generated owing to electromagnetic induction, and thenthe relative displacement between the coils and the magnets aregenerated. The variable relative displacement is regulated by theelectric current.

[0007] The conventional drivers have several drawbacks. The magneticforce lacks the linear characteristic, so that it is difficult for thedrivers to precisely direct the read/write heads to the workingpositions.

[0008] For example, the movable member V shown in FIG. 3 for carryingthe objective lens and the coils wound thereon should be produced inadvance in the fabricating process. The fabricating process iscomplicated, and the coils are wounded on the movable member withdifficulty. It is more complicated that the coils are wound in advance,and then fixed to the movable member.

[0009] For the moving magnets type drivers, the permanent magnets M1 andM2 are connected with the movable member V shown in FIG. 4. However, themagnets are much heavier than the coils, so that the sensitivity and theprecision of the driver are reduced due to the heavy weight.

[0010] In order to overcome the foresaid drawbacks, the presentinvention provides a magnetic device for being used in a driver.

SUMMARY OF THE INVENTION

[0011] It is therefore an object of the present invention to provide amagnetic device for being used in a driver.

[0012] In accordance with the present invention, the magnetic deviceincludes a permanent magnet unit, a first yoke unit positionedcorresponding to the permanent magnet unit, a second yoke unit havingone end connected with the first yoke unit, and a coil complex having adouble-cross type for generating magnetic force.

[0013] The permanent magnet unit, the first yoke unit and the secondyoke unit are used for generating a magnetic circuit, and the magneticforce generated from the coil complex interacts with the magneticcircuit.

[0014] Preferably, the permanent magnet unit has a plurality ofpermanent magnets.

[0015] In accordance with the present invention, the coil complexincludes a first coil unit wound around the second yoke unit, and asecond coil unit perpendicularly wound around the first coil unit.

[0016] The magnetic force generated by the first coil unit interactswith the magnetic circuit to generate a first force for movement in afirst direction.

[0017] The magnetic force generated by the second coil unit interactswith the magnetic circuit to generate a second force for movement in asecond direction.

[0018] The first direction is perpendicular to the second direction.

[0019] Preferably, the first coil unit has a plurality of focusingcoils, and the second coil unit has a plurality of tracking coils.

[0020] Preferably, the first coil unit is a focusing coil, and thesecond coil unit has two tracking coils. The two tracking coils arewounded around two ends of the focusing coil to form the double-crosstype.

[0021] Preferably, the driver is an optical read/write head having amovable member. The coil complex is connected with the movable member.The movable member has an objective lens thereon.

[0022] The present invention may best be understood through thefollowing descriptions with reference to the accompanying drawings, inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIGS. 1 to 4 are schematic views showing the conventionalobjective lens drivers;

[0024]FIG. 5 is the schematic view showing the magnetic device accordingto the first preferred embodiment of the present invention;

[0025]FIG. 6 is the schematic view showing the magnetic device accordingto the second preferred embodiment of the present invention;

[0026]FIG. 7 is the schematic view showing the magnetic device in FIG. 6applied in an objective lens driver according to the present invention;

[0027]FIG. 8 is the schematic view showing the magnetic device accordingto the third preferred embodiment of the present invention; and

[0028]FIG. 9 is the schematic view showing the magnetic device in FIG. 8applied in an objective lens driver according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] The present invention provides a magnetic device for being usedin a driver. A specific combination of a coil complex having adouble-cross type and yokes having a specific appearance are used forgenerating the magnetic force having a better linear characteristic toimprove the sensitivity of the driver and simplify the fabricatingprocess of the driver.

[0030] Please refer to FIG. 5. M_(a) is a permanent magnet. The trackingcoils T_(a) and T_(b) are wound around the focusing coil F_(a) to form adouble-cross coil complex. A fixed yoke Y_(b) is further contained inthe coil complex, and the fixed yoke Y_(b) is connected with a fixedyoke Y_(a) outside the coil complex. The magnetic lines of force aredistributed in the yokes Y_(a) and Y_(b). The magnetic force generatedby the tracking coils T_(a) and T_(b) interacts with the magneticcircuit generated by the permanent magnets and the yokes to generate amagnetic force along the X axis. The magnetic force generated by thefocusing coils F_(a) interacts with the magnetic circuit to generated amagnetic force along the Z axis.

[0031] The present invention provides a magnetic device having a simplerstructure than the conventional device. The coil is wound individually,and the wound coils are combined with the yokes. The fabricating processof the device is simplified. Furthermore, the movable member is lighterthan the conventional device, so that the sensitivity is better than theconventional device.

[0032]FIG. 6 is a schematic view showing the magnetic device accordingto the second preferred embodiment of the present invention. The yokesY_(c) and Y_(d) respectively have a half volume of the yokes Y_(a) andY_(b) shown in FIG. 5, and the Hence, the effect of the device is notreduced. Hence, the magnetic device further provides an advantage thatthe material of the device is reduced. FIG. 7 is a schematic viewshowing the magnetic device further including the movable member V_(a)and the objective lens O.L.

[0033]FIG. 8 is a schematic view showing the magnetic device accordingto the third preferred embodiment of the present invention. Thepermanent magnets M_(c) and M_(d) and the yokes Y_(e), Y_(f) and Y_(g)are used in the magnetic device. FIG. 9 is a schematic view showing themagnetic device further including the movable member V_(a) and theobjective lens O.L.

[0034] The present invention has the advantage as follows.

[0035] 1.) The present invention is used for generating the magneticforce having a better linear characteristic to improve the sensitivityof the driver.

[0036] 2.) The present invention provides a simpler fabricating processof the driver than the conventional driver.

[0037] 3.) The present invention is used for reducing the material cost.

[0038] While the invention has been described in terms of what arepresently considered to be the most practical and preferred embodiments,it is to be understood that the invention need not be limited to thedisclosed embodiment. On the contrary, it is intended to cover variousmodifications and similar arrangements included within the spirit andscope of the appended claims which are to be accorded with the broadestinterpretation so as to encompass all such modifications and similarstructures. Therefore, the above description and illustration should notbe taken as limiting the scope of the present invention which is definedby the appended claims.

What is claimed is:
 1. A magnetic device for being used in a driver,comprising: a permanent magnet unit; a first yoke unit positionedcorresponding to said permanent magnet unit; a second yoke unit havingone end connected with said first yoke unit; and a coil complex having adouble-cross type for generating magnetic force, wherein said permanentmagnet unit, said first yoke unit and said second yoke unit are used forgenerating a magnetic circuit, and said magnetic force generated fromsaid coil complex interacts with said magnetic circuit.
 2. The magneticdevice according to claim 1, wherein said permanent magnet unit has aplurality of permanent magnets.
 3. The magnetic device according toclaim 1, wherein said coil complex comprises: a first coil unit woundaround said second yoke unit; and a second coil unit perpendicularlywound around said first coil unit.
 4. The magnetic device according toclaim 3, wherein said magnetic force generated by said first coil unitinteracts with said magnetic circuit to generate a first force formovement in a first direction.
 5. The magnetic device according to claim4, wherein said magnetic force generated by said second coil unitinteracts with said magnetic circuit to generate a second force formovement in a second direction.
 6. The magnetic device according toclaim 5, wherein said first direction is perpendicular to said seconddirection.
 7. The magnetic device according to claim 3, wherein saidfirst coil unit has a plurality of focusing coils.
 8. The magneticdevice according to claim 3, wherein said second coil unit has aplurality of tracking coils.
 9. The magnetic device according to claim3, wherein said first coil unit is a focusing coil.
 10. The magneticdevice according to claim 9, wherein said second coil unit has twotracking coils.
 11. The magnetic device according to claim 10, whereinsaid two tracking coils are wounded around two ends of said focusingcoil to form said double-cross type.
 12. The magnetic device accordingto claim 1, wherein said driver is used in an optical read/write headhaving a movable member.
 13. The magnetic device according to claim 12,wherein said coil complex is connected with said movable member.
 14. Themagnetic device according to claim 13, wherein said movable member hasan objective lens thereon.